Radio frequency (RF) filters are an important component in modern communication systems. With the growing number of bands and modes of communications, the number of RF filters in a mobile device front end can multiply quickly. Resonators, such as film bulk acoustic resonators (FBAR), sometimes referred to as thin-FBAR (TFBAR), are the components that are used to make RF filters. For example, one RF filter may include up to seven FBAR devices arranged in various configurations (e.g., a half-ladder circuit configuration). An FBAR or TFBAR is a device consisting of a piezoelectric material located between two electrodes and acoustically isolated from the surrounding medium. An example RF front end covering 2G/3G and 4G mobile telecommunications technologies may contain seventeen RF filters, which can result in a total of 119 FBARs, for example.
These and other features of the present embodiments will be understood better by reading the following detailed description, taken together with the figures herein described. In the drawings, each identical or nearly identical component that is illustrated in various figures may be represented by a like numeral. For purposes of clarity, not every component may be labeled in every drawing. Furthermore, as will be appreciated, the figures are not necessarily drawn to scale or intended to limit the described embodiments to the specific configurations shown. For instance, while some figures generally indicate straight lines, right angles, and smooth surfaces, an actual implementation of the disclosed techniques may have less than perfect straight lines and right angles, and some features may have surface topography or otherwise be non-smooth, given real-world limitations of fabrication processes. In short, the figures are provided merely to show example structures.